Recently I reviewed my google earth models (or better: 3D warehouse models) and checked on the license that is bound to them.
My conclusion: google and anyone wo gets a license from google may do anything with may models, but I'm not allowed to use (= create derivative works and redistribute) other models than those I created myself.

While I have no problem with my models being used by others (even commercial), I have a problem with not giving everyone the same amount of fair access. I would really like to publish them under CC_by_SA or even Public Domain. I can actually do that, as the license granted to google is 'non-exclusive', I just can't do it in googles warehouse.

Wouldn't it be nice to publish them (at least geo-referenced models of real world buildings) through openstreetmap? Even if we don't display them yet, it would be a great place of storing them and making them available to everyone.

There are some slight discussions (mostly outdated) about that in the wiki, but I haven't found any definitive answer.
Is there somebody with insight into the server hard- and software who could tell if it's even possible to store 3D (Collada?) models on them? Maybe just 3D data without textures?

Or does someone know a wiki page or blog entry that deals with that matter?

From a technical point of view, the existing OSM database is probably not useful for storing building, as models are very different from the current data format. However, the OSM *project* could likely use the building models, and it would also make sense to create links between the OSM database and the building models to allow for seamless integration.

Ideally, we would set up a separate database/server dedicated to storing building models under a free license (maybe CC-BY-SA, with the option to grant a more liberal license - similar to Wikimedia image licensing choices). That database should provide the possibility to retrieve building models based on a coordinate range and should store references to objects in the OSM database with an appropriate addressing mechanism. Building such a database certainly appears to be a manageable task - someone would just have to do it...

Actually, I'm very interested in the availability of 3D models myself because I'm currently creating a converter that transforms OSM map data into 3D scenes, and models for individual buildings would make a great addition to that. However, it will likely take me a few more months to get to the stage where all the core OSM features work well enough for me to consider the next step, i.e. integrating building models.

Yea, I probably threw the osm database and the osm project together. I will dig a bit deeper at whom to contact about that.

Besides the pure 3D data (which essentially is just vector data), there will be texture data which probably takes up quite an amount of disc space and therefore bandwidth. I don't know if and how a donation-funded organisation as OSM can handle this.

The needed metadata is minimal. Google stores the coordinates as 3D, but usually leaves the z axis at zero and just ticks a 'at ground level' property. The scale conversion would need to be done in the viewing application. The 3D data usually contains scale information for that. Google adds some camera position and tilt/yawn information, but that's optional.

But there is another problem: "Without Google’s prior written authorization, you may not use or distribute a Photo Textures Model in a mapping or geographic application or service (other than a Google Service)" In context this probably only applies to photo textures created with street view imagery, but followed to the letter this means you can't use models in OSM.

I went to look at the TOS, but this version: http://sketchup.google.com/intl/en/3dwh/tos.html doesn't contain the reference to "Photo Textures Model". It must be a defined term and I assume it must refer only to streetview imagery (where Google has copyright). They can't restrict what you do with a textured model where you own the texture photos.
To be compatible with OSM, the georeferencing should be derived from OSM, not Google Maps, otherwise you could be falling foul of "you may not: (ii) use or distribute Content obtained from Google Services in a mapping or geographic application or service." and general copyright issues.

There is www.osm-3d.org if you are looking in bigger towns e.g. Rostock you see a very low poly L1 model by extruding the building ways.

To get a higher level of details we would need 3D infrastructure that is able to store general models (e.g. a german bus station looks generally like this....) and that is able to respecify it for a given area (a bus station here in Rostock looks like this...).